/* Copyright 1998 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */

/*
 * ares_parse_ns_reply created by Vlad Dinulescu <vlad.dinulescu@avira.com>
 *      on behalf of AVIRA Gmbh - http://www.avira.com
 */

#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#else
#include "nameser.h"
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif

#include "ares.h"
#include "ares_dns.h"
#include "ares_private.h"

int ares_parse_ns_reply(const unsigned char* abuf, int alen,
    struct hostent** host)
{
    unsigned int qdcount, ancount;
    int status, i, rr_type, rr_class, rr_len;
    int nameservers_num;
    long len;
    const unsigned char* aptr;
    char *hostname, *rr_name, *rr_data, **nameservers;
    struct hostent* hostent;

    /* Set *host to NULL for all failure cases. */
    *host = NULL;

    /* Give up if abuf doesn't have room for a header. */
    if (alen < HFIXEDSZ)
        return ARES_EBADRESP;

    /* Fetch the question and answer count from the header. */
    qdcount = DNS_HEADER_QDCOUNT(abuf);
    ancount = DNS_HEADER_ANCOUNT(abuf);
    if (qdcount != 1)
        return ARES_EBADRESP;

    /* Expand the name from the question, and skip past the question. */
    aptr = abuf + HFIXEDSZ;
    status = ares__expand_name_for_response(aptr, abuf, alen, &hostname, &len);
    if (status != ARES_SUCCESS)
        return status;
    if (aptr + len + QFIXEDSZ > abuf + alen) {
        ares_free(hostname);
        return ARES_EBADRESP;
    }
    aptr += len + QFIXEDSZ;

    /* Allocate nameservers array; ancount gives an upper bound */
    nameservers = ares_malloc((ancount + 1) * sizeof(char*));
    if (!nameservers) {
        ares_free(hostname);
        return ARES_ENOMEM;
    }
    nameservers_num = 0;

    /* Examine each answer resource record (RR) in turn. */
    for (i = 0; i < (int)ancount; i++) {
        /* Decode the RR up to the data field. */
        status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len);
        if (status != ARES_SUCCESS)
            break;
        aptr += len;
        if (aptr + RRFIXEDSZ > abuf + alen) {
            status = ARES_EBADRESP;
            ares_free(rr_name);
            break;
        }
        rr_type = DNS_RR_TYPE(aptr);
        rr_class = DNS_RR_CLASS(aptr);
        rr_len = DNS_RR_LEN(aptr);
        aptr += RRFIXEDSZ;
        if (aptr + rr_len > abuf + alen) {
            ares_free(rr_name);
            status = ARES_EBADRESP;
            break;
        }

        if (rr_class == C_IN && rr_type == T_NS) {
            /* Decode the RR data and add it to the nameservers list */
            status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
                &len);
            if (status != ARES_SUCCESS) {
                ares_free(rr_name);
                break;
            }

            nameservers[nameservers_num] = ares_malloc(strlen(rr_data) + 1);

            if (nameservers[nameservers_num] == NULL) {
                ares_free(rr_name);
                ares_free(rr_data);
                status = ARES_ENOMEM;
                break;
            }
            strcpy(nameservers[nameservers_num], rr_data);
            ares_free(rr_data);

            nameservers_num++;
        }

        ares_free(rr_name);

        aptr += rr_len;
        if (aptr > abuf + alen) { /* LCOV_EXCL_START: already checked above */
            status = ARES_EBADRESP;
            break;
        } /* LCOV_EXCL_STOP */
    }

    if (status == ARES_SUCCESS && nameservers_num == 0) {
        status = ARES_ENODATA;
    }
    if (status == ARES_SUCCESS) {
        /* We got our answer.  Allocate memory to build the host entry. */
        nameservers[nameservers_num] = NULL;
        hostent = ares_malloc(sizeof(struct hostent));
        if (hostent) {
            hostent->h_addr_list = ares_malloc(1 * sizeof(char*));
            if (hostent->h_addr_list) {
                /* Fill in the hostent and return successfully. */
                hostent->h_name = hostname;
                hostent->h_aliases = nameservers;
                hostent->h_addrtype = AF_INET;
                hostent->h_length = sizeof(struct in_addr);
                hostent->h_addr_list[0] = NULL;
                *host = hostent;
                return ARES_SUCCESS;
            }
            ares_free(hostent);
        }
        status = ARES_ENOMEM;
    }
    for (i = 0; i < nameservers_num; i++)
        ares_free(nameservers[i]);
    ares_free(nameservers);
    ares_free(hostname);
    return status;
}
